Hair of the dog

I see that New Jersey will be passing out potassium iodide pills as a precaution against various types of radiological terror.

The devil in me makes me point out that these pills will be radioactive.

Why? The potassium. About a percent or so of all potassium is a radioactive isotope. Sic a Geiger counter on some salt substitute (potassium chloride) and you'll see what I mean (you have a Geiger counter laying around, don't you?)

Of course potassium is essential to your body, particularly for your heart. So if your body can't handle some radiation, it's a pretty bad design, eh?

UPDATE: The percentage of radioactive potassium found in naturally occurring potassium is significantly smaller than "a percent or so" as mentioned above. According to this PDF it's about .012%. The idea is the same though.

There's other interesting stuff in that PDF, such as this:

Hence, the potassium-40 content in the body is constant, with an adult male having about 0.1 microcurie (µCi). Each year, this isotope delivers doses of about 18 millirem (mrem) to the soft tissues of the body and 14 mrem to bone.

That's just from living, folks - if you're a human being you have no practical way to avoid it. Keep those numbers in mind the next time someone wants to spread radiological terror.